Message of The Day
Message of the Day, or MOTD, refers to the line in a server's configuration that shows up on the load screen when a player connects. On a non-modded Base server, this can only be one line and changed in the configuration, which then requires a server restart to show the change.
In many server-side mods like JA+ the MOTD can be many lines of text, and also display to the player when they join the actual game. These are typically used to display the many rules of the server and advertise a clan's website and recruitment.